Electronic high-voltage regulator



0st 26, 1948. G. W. CQOK 2452 037 ELECTRONIC HIGH-VOLTAGE REGULATOR Filed way 19, 194'? INVENTOR. George W- Dunk BY ATTORNEY.

Patented Got. 26, E948 UNETE$ STATES PATENT (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 3 Claims.

The invention relates to improvements in voltage regulators and more particularly to an improved electronic regulator for high voltages.

Conventional electronic voltage stabilizing circuits are generally limited in application to the design of regulators for relatively low output potentials. In order to adaptvoltage stabilizing circuits of the series regulator-tube type to the control of output potentials between 100 and 400 volts, it is necessary only to provide a suitable voltage supply and to apportion the battery voltages properly. Receiving-type radio tubes which are readily available may be used. Moreover, the coupling batteries can easily be eliminated at these low voltages by the use of voltage dividers and gaseous regulator tubes.

But when potentials of 2000 volts or more are required at the output terminals, the difliculties in regulator circuit design mount enormously.

Proper operating potentials for the amplifier tube place its control grid about 200 volts negative with respect to the positive output terminal of the regulator, thus leaving a potential difference of 1800 volts between the cathode of the amplifier and the negative terminal of the regulator.

The use of batteries as a coupling between the cathode of the amplifier tube and the negative terminal of the regulator presents a problem because of the bulk required to make up the potential difference.

If gas tubes are used, 15 to 30 of the types now commercially available are required to subtend the potential difference. The total resistance of such a series is relatively high, and reduction in the voltage gain of the amplifier by degeneration is noticeable. Also occasional sparkover during starting and the need for frequent replacement of gas tubes are sources of annoyance.

A variety of schemes have been tried with more or less success, but a special type of coupling device is nevertheless needed for this particular application. Clearly this coupling device must accommodate any initial D.-C. potential difference across itself and still afford a direct-coupled signal path between the amplifier cathode and the negative terminal of the regulator. It must of course have a low dynamic resistance and must take up very little space.

An important object of the present invention is the provision of a series-type voltage regulator having a special coupling between the amplifier or control tube and the negative supply line which will permit the efiective regulation and control of high voltages without resort to the use of transmitting-type tubes with their attendant wastage 2 of electrical power, high-voltage batteries, or a series of gas tubes.

Another object is to provide a high-voltage regulator which is compact, simple in operating principle and effective.

Other objects and advantages of the invention will become apparent during the course of the following detailed description, taken in connection with the accompanying drawing, forming a' part of this specification and in which drawing:

Figure 1 is a diagrammatic view of the improved regulator circuit.

Figure la is a view showing a modified portion of the circuit.

Referring to Figure 1, the positive and negative input terminals Hi, ll of the regulator are intended for connection to a D.-C. source of approximately 3000 volts, and the positive and negative output terminals l2, l3 are for connection to a load requiring a potential of 2500 volts.

Connected in the positive line between the voltage source and the load is a cathode-follower tube I4 having its grid subject to the controlling action of a pentode amplifier IS. The screen grid and as a. change in grid bias on the amplifier tube l5.

The amplifier plate current flows through a, plate load resistor 25 that fixes the biasing voltage on the grid of the series tube 54.

The coupling means 24 also includes a constantcurrent device of the type disclosed in my U. S. Patent 2,369,138, dated February 13, 1945. This constant-current device employs a current-limiter triode 26 having its cathode connected through a cathode-load resistor 2? to the negative terminal of a 250-volt battery 25 whose positive of the triode 26 and the positive output terminal i2 is a series of resistors iiii l2 which develop the necessary control potential at the cathode of The correct value the current-limiter tube 26.

of the resistor series 36-42 for constant current in the plate circuit of the triode 26 is equalto mu times the value of the resistor 21 where mu is the amplification factor of the tube 25 under its operating conditions. The control grids of the tubes 18-23 are connected at the negative sides of the plate load resistors 30-35 respectively, of the current-limiter tube 26, as shown.

In describing the operation of the coupling system when an abrupt change in load current tends to produce a momentary increment in output voltage, it is convenient to assume that the negative output terminal l3 Of the ::egu1ator is a fixed potential-reference point and that the increment is a change in potential on the positive output terminal I2 relative to the reference point is.

A constant current is maintained in the resistor network 30-35 by the current-limiter tube 25. By virtue of the constant current in this resistor network, any increment produced at the output terminal l2 appears unattenuated at the plate of the limiter tube 26. In transmission down the resistor network 30-35, this voltage increment is impressed equally on the control grids of the tubes l 5 and Ill-23.

A plate-current change is induced in the triode tube 23 by the application of the voltage in-- crement to its control grid. A similar platecurrent change is induced in the triode tube 22, since the same voltage increment is applied to its control grid. The inverted signal which would normally be produced at the plate of the triode 23 acting as an amplifier is exactly balanced by'the uninverted signal produced at the same point by the triode 22 acting as a cathode follower. The plate of the triode 23 is then established as a fixed-potential point relative to the negative terminal l3 of the regulator.

Once this plate-cathode juncture has been established as a fixed-potential point, it is clear that the next similar juncture between tubes 2|, 22 is also a fixed-potential point. Likewise, progressively up this series of triode tubes, each successive plate-cathode juncture can be shown to be a fixed-potential point, provided that the voltage increment is applied simultaneously to all control grids of the series. 7

The series of fixed-potential points does not include the cathode of the pentode amplifier tube 15. The presence of the load resistor 25 in the plate circuit of this tube increases the efiective dynamic resistance at the cathode.

The amplifier action of the triode l8 exceeds the cathode-follower action of the pentode and a small inverted signal appears at the cathode. This inverted replica of the output voltage increment adds to the original increment already coupled to the control grid by the coupling resistor I! in developing an increased grid-tocathode voltage for theamplifier tube. The effective voltage gain of this amplifier stage is thereby enhanced.

It would have been suflicient if the coupling system had established the' cathode of the amplifier tube l5 as a fixed-potential point with respect to the negative terminal l3. In that case the dynamic resistance of .the coupler would have been equal to zero. Actually the action of the coupling device is such that the dynamic resistance is slightly negative. The addition of a suitable cathode resistor 43 to the triode 23 as shown in Figure 1a makes the incremental resistance of the coupler zero.

The overall effectiveness of a series-type regmeans connecting the amplifier anode to the ulator in maintaining its output potential is determined almost entirely by the magnitude of the voltage gain that can be developed in the amplifier stage. Since the use of the coupling device just described actually increases the normal voltage gain of the amplifier, the performance characteristics of the high-voltage regulator circuit compare favorably with those of lowvoltage regulators.

Any initial voltage drop across the device can be accommodated simply by increasing or decreasing the number of tubes and resistors in the circuit. The potential difference across any one tube can well be 300 volts or less. which is within the safe operating range recommended by the tube manufacturers for receiving-type radio tubes.

In the final circuit design, the batteries it and 28 may be replaced by suitable voltage regulators; and capacitors t l-50 of moderate capacity are placed across the resistors l1 and 3l-36, respectively, of the constant-current network. These capacitors not only serve to ensure good high-frequency transmission characteristics for the network, but also provide adequate icy-passing capacity to reduce the effects of spurious currents in the network that are induced by capacity to adjacent circuit components. Also it is preferred to provide separate heaterexcitation for each of the tubes to prevent harmful potential differences between the respective heaters and cathodes.

The output voltage of the regulator circuit'is very nearly equal to the algebraic sum of three voltages: (1) the voltage across resistor ll; (2) the bias voltage between the cathode and control grid of the amplifier I5; and (3) the voltage drop across the series of resistors 30-35. The voltage drop across the resistor series 30-35 is determined by the current in the limiter tube 26. The grid-biasing voltage on this tube is adjustable at the potentiometer 29. The current in this tube and in the resistor series 30-35 is related directly to the setting of the potentiometer. The range of the potentiometer is such that the output voltage of the regulator may be set to any value between 1000 and 2500 volts by suitable manipulation of the potentiometer contact 5|.

' Although the coupling system has been described in connection with a regulator having a maximum output potential of about 2500 volts, it is reasonable to assume that the practical limit to its use for still higher voltages may be determined by consideration of insulation requirements.

Various changes may be made in the forms of invention herein shown and described without departing from the spirit of the invention or the scope of the following claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

Iclaim:

1. An electronic regulator for stabilizing the voltage supplied by a direct-current source through positive and negative lines to a load, comprising an electron tube having at least a cathode, anode and control electrode, said tube being serially connected in the positive lin to act as a regulator, an amplifier tube having at least a cathode, anode and control electrode,

positive line, means applying to the control electrode oi the series tube a bias of a magnitude which is a i'unction of the amplifier anod current, means applying to the amplifier control electrode a bias which varies with changes in load voltage, a series of grid-controlled electron tubes connected between the amplifier cathode and the negative line for accommodating a high potential diiierence therebetween, and means fixing the incremental resistance of said series of tubes at a value substantially no greater than zero comprising a series of resistors coupling the control rids of said series of tubes with the control electrode of said amplifier tube, and a device maintaining constant current in said resistor series whereby a signal potential impressed on the control electrode of the amplifier tube will be simultaneously applied without attenuation to the control grids of said series of tubes.

2. An electronic regulator according to the preceding claim, including means for adjusting said constant-current device so that the voltage drop across said series 0! resistors may be changed thereby to vary the output voltage of the regulator.

3. An electronic regulator for stabilizing the voltage supplied by a direct-current source through positive and negative lines to a load, comprising an electron tube having at least a cathode, anode and control electrode, said tube being serially connected in the positive line to act as a regulator, an amplifier tube having at least a cathode, anode and control electrode, means connecting the amplifier anode to the positive line, means applying to the control electrode of the series tube a bias of a magnitude which is a function of the amplifier anode current, means applying to the amplifier control electrode a bias which varies with changes in load voltage, a series of grid-controlled electron tubes connected between the amplifier cathode and the negative line for accommodating a high potential difference therebetween, and means fixing the incremental resistance of said series of tubes at a value substantially no greater than zero comprising a series of resistors coupling the control grids of said series of tubes with the control electrode of said amplifier tube, a device maintaining constant current in said resistor series whereby a signal potential impressed on the control electrode of the amplifier tube will be simultaneously applied without attenuation to the control grids of said series of tubes, and capacitors connected across the resistors of said series.

GEORGE W. COOK.

REFERENCES CITED UNITED STATES PATENTS Name Date Brewer Apr. 23, 1946 Number 

